Resistance coating for articles of glassware and the like



April 6, 1965 c. M. DE WOODY ETAL 3,177,341

RESISTANCE COATING FOR ARTICLES OF GLASSWARE AND' THE LIKE Filed March 12, 1963 INVE N T 0R3 0mm. E5 M. oswooor A TTORNE Y United States Patent 3,177,341 RESISTANCE COATDIG FUR ARTICLES 0F GLASSWARE AND Tim LIKE Charles M. De Woody, Rascal L. Pearce, and Walter Mueller, Cumberland County, and Eugene A. Egizi,

I Camden County, N..ll., assignors to Ace Giass linearporated, Vinelaud, NA, a corporation of New .lersey Filed Mar. 12, 1963, Ser. No. 264,489 8 Claims. (Cl. 219385) This invention relates to the field of laboratory glassware and the like, and consists more particularly in new and useful improvements in an electrical resistance coating for heating glassware, the present application being a continuation-in-part of copending application Serial No. 862,331, filed December 28, 1959, now Patent No. 3,092,- 704, issued June 4, 1963.

As in said copending application, the primary object of the invention is to provide economical means for heating glassware and the like, by selectively distributing the current in a resistance coating applied to the periphery of the glassware.

Another object is to provide a heating vessel capable of producing higher temperatures with greater safety than is possible with conventional equipment.

Still another object of the invention is to provide a resistance coating for heating vessels and the like, designed to minimize the occurrence of hot spots which cause cal superheating and/ or to provide desirable temperature gradients.

A further object is to provide a unit of glassware having an integral heating means incorporated therein in the form of a resistance coating to thereby facilitate convenience of use.

Still another object of the invention is to provide a resistance coating for heating glassware, comprising broad bands of resistance material to obtain a maximum surface coverage, and simultaneously provide basic circuitry for more accurate control of the distribution of current in both symmetrical and non-symmetrical objects While applying a practically uniform thickness of coating of resistance material, when desirable, at least one form of said coating being capable of producing high temperatures with low voltage inputs and providing practically instantaneous response to voltage changes.

Another object is to provide a resistance coating for vessels, comprising broad bands of resistance material including means for providing shunt circuits or short circuits at selected locations to minimize the development of hot spots and/ or to provide desirable temperature gradients.

A still further object of the invention is to provide a unit of glassware having a resistance coating and an integral insulation having heat and chemical resistant properties.

The primary object of the particular phase of the invention covered by this continuation-in-part is to provide means for positively locating and retaining the electrical contacts necessary for energizing the resistance coating applied either to the outer or inner peripheries of the vessel or both.

In this connection, it is an object of this invention to provide suitable peripheral grooves in the vessel to accommodate and anchor electrical terminal means, such as contact ring connectors, so as to afford positive contact, especially in inaccessible areas.

, A further object of the invention is to provide terminal ring locating and retaining grooves which coact with supporting clamps for supporting and energizing a resistance coated unit of glassware.

Still another object of the invention is to provide terminal retaining grooves which greatly facilitate the application and removal of terminal rings, and are especially helpful when cleaning the apparatus in preventing damage to the power leads.

Another object of the invention is to provide terminal ring retaining grooves which also serve to define the resistance coating limits so as to facilitate the application of the conducting coating to the periphery of the vessel.

With the above and other objects in view which will appear as the description proceeds, the invention consists in the novel features herein set forth, illustrated in the accompanying drawings, and more particularly pointed out in the appended claims.

Referring to the drawings in which numerals of like character designate similar parts throughout the several views:

FIG. 1 is a perspective view of a laboratory beaker representing one unit of glassware embodying the present invention, the insulating jacket being broken away to show the resistance coating;

FIG. ,2 is a view of said beaker in side elevation, showing the support-clamp and electrical contacts in dotted lines;

FIG. 3 is a plan view of one form of support-clamp contacts, showing the beaker in dotted lines;

FIG. 4 illustrates a modification in the application of the resistance coating, as viewed from the bottom of a unit of glassware;

FIG. 5 shows one form of the application of terminal grooves to the external periphery of a tube-like vessel or column embodying the present invention;

FIG. 6 is a similar veiw showing the application of terminal grooves to the internal periphery of a column; and

FIG. 7 illustrates a modified form of the invention, wherein terminal grooves are provided both on the external and internal peripheries of a column to which the resistance coating is applied both internally and externally in a continuous coat.

Briefly, the invention consists in applying to the periphery of a unit of glassware or similar normally non-con ducting surface, a film or coating of resistance material arranged in a complete conducting circuit. This resistance material, as will later appear, may be applied either to the inner or outer periphery of the vessel or both, as a continuous coating, or arranged in one or more broad bands which are discontinuous around the periphery and/ or intercepted by integral shunt configurations, and which have terminal and/ or integral shunt means which are discontinuous around the major periphery, said terminal and shunt means being preferably formed of a metallic coating of lesser resistance, and the terminal means adapted to receive opposed contact members or electrodes between which electrical current flows to heat the unit in a controlled pattern of heat intensity.

Considering the invention in greater detail and referring first to FIGS. 1 and 2, the vessel, in this case a beaker, is generally represented by the numeral 11 and may be formed of any suitable laboratory-type glass, such as Pyrex 7740 glass. A thin coating or film of electrical resistance material 12 is applied to the periphery of the beaker 11 in the form of two broad peripheral bands 12a and 12b, separated from one another on opposite sides of the beaker by longitudinally extending gaps or spaces 13, running down the side walls of the beaker and partially across the bottom, so as to leave an uninterrupted connecting area 14 which completes the conducting circuit, as will later appear.

Adjacent the upper boundaries of the bands 12a, 12b, the beaker 11 may be circumferentially recessed to provide grooves 15:: and 15b, and the surfaces of these grooves are coated with a metal of less resistance than the coating '12. The metallic coatings of the grooves ing bands d241, 1211 and form opposite terminals for the conducting circuit. Preferably, the adjacent ends of the grooves 15a, .1512 are separated by glass knobs or crimps 16 which not only insure the isolation of the respective terminals, but facilitate the installation and positioning of the electrical contacts which are received by the grooves 15a, 15b as hereinafter. referred to.

treferably, the resistance coating 12' consists of platinum applied by spraying one or more coats of a solution containing platinum and baking in an oven at temperatures in excess of 1160" F. after the coating is dried. The thickness of the resulting metallic platinum or platinum alloy coating may vary but generally should not exceed .0015 inch and should not be less than .0003 inch.

It will be understood that while platinum is preferred,

various other metals such as silver, tin aluminum and gold may be used, the thickness of which will vary with the metal used. For instance, a coating resulting from a tin salt may be in the order of 0.000016 inch.

The terminal coatings such as in grooves 15a, 15b and shunt coatings '13 are preferably of silver and of a thickness in the order or 0.008 inch and generally not less than 0.603 inch. 111 any event, the thickness of the terminals should be greaterthan that of the coating 12,. and, if

desired, the terminal coating may be of the same material as that employed in the resistance coating, but in this case,

the subsequent coats are applied in localized, well-defined, geometric patterns.

The application of current through the contacts or electrodes 17a, 17b to the terminals 15a, 15]) results in current flowing down one of the bands of resistance material 12, across the bottom area 114, and up the other band, and for the duration of the flow of current through this circuit, the resistance coating 111-2 causes the uni-form heating of the beaker throughout its coated cylindrical contour, and a more intense heating of the bottom contours because of the narrowed band in this section.

It is desirable to have a lower temperature on the side walls in vessels where evaporation is caused in order to reduce or eliminate decomposition of material spattered thereon in the course of evaporation. The temperature of the bottom is therefore raised in relation to the upper walls by narrowing the resistance band.

However, when current flow is relatively high, such as in the passage of 5 amperes or more through the narrowed portion, or connecting passage, hot spots tend to develop adjacent the extremities of the gaps 13. In order to obviate this dii'hculty, it has been found that by providing a shunt circuit or short circuit at selected locations adjacent the gap betweenthe coating bands 12a. and 12b, and establishing an area of reduced resistance where the overheating would most likely occur, the current is caused to Dy-pass through the lesser resistance and induce a cooling effect in the area around it. As shown in FIG. 1, at the lower extremity of each of the gaps 13, an area 13 on the surface of the glass beaker bottom is coated with silver of a thickness substantially the same as the silver coating of the terminal grooves 15a, 1512. Thus, with the resistance at these points reduced, the current by-passes the critical area and at the same time, is redistributed over substantially the entire bottom, forming straight line paths to the terminal bands 15a, 15'!) on the side walls of the beaker.

An insulating jacket 19 overlying the coating 12 completes the unit. t'fhis jacket is preferably formed by dipping the resistance coated vessel in silicone rubber catalyzed latex and curing to a resilient form with heat, or applying any suitable high temperature electrical insulation, such as a ceramic glaze or silicone resin. Silicone rubber has been found to possess the desired insulating properties and its resilience also serves the added purpose of protecting the glassware against breakage. However, other materials having these properties could obviously be used.

Depending upon the intended use of the article of glassware, the system of forming the bands of resistance material and the shunt circuits is subject to numerous variations. For example, FIG. 4 shows a generally similar resistance coating for a beaker, round bottom flask, culture dish, or similar article, but instead of'providing an uninterrupted resistance coating area such as 1 in 'FIG. 1, this modified form comprises two completely separated coating bands 112a, 1212 spaced by a continuous gap 1? which extends down both sides of the vessel and across At the same time, the shunt circuit 18, being of lesser 7 so that when they are inserted in the respective grooves,

resistance than the bands 12a, 12b provides an area of reduced resistance where the overheating of the vessel would most likely occur and prevents the development of hot spots in the bottom of the vessel, while simultaneously providing a temperature gradient which is substantially unirorm.

Turning now to FIG. 5, which diagrammatically illus hates the terminal groove arrangement as applied to a' tubular article of glassware such as a column, 11a represents the column per so, having a pair of vertically spaced peripheral grooves 150 and 15d in its outer periphery. The outer periphery of the column lie is entirely covered between the upper and lower grooves 150 and 15d with resistance material d-Zc, similar to that employed in the vessel shown in FIG. 1, and the terminal grooves may be lined with this same material or, as in the structure shown in FIG. 1, their inner surfaces may be coated with a metal of less resistance than the coating 12c. Inasmuch as the resistance material is applied to the external surface of the column shown in FIG. 5, this coating is preferably covered by an insulator coating 19a, similar to the coating '19 in FIG. '1. The insulator coating 19a terminates just short of the grooves 150 and 15:! as at 1%, to provide access for the terminal electrodes or contacts 176 and 17d respectively.

These contacts are preferably, in the form of a split ring of conducting material under a normal inward tension so that they will easily snap into their respective grooves 15c and 15d in firm contact with the conductive lining of said grooves. Thus, when the contacts 170 and 17d are energized, an electric circuitis completed through the resistance coating on the outer periphery of the column lla.

In some instances, it may be desirable to provide the resistance coating and terminal contact retaining grooves on the inner surface of a tube or column 31a and such an embodiment'is shown in FIG.v 6. 'Here it will be seen that the inner periphery of the column is coated with resistance material 12d and the inner surfaces of the vertically spaced grooves and 15d are coated with conducting material, as previously described. In this form of the invention, split contact rings 17c and 17d are of the type which are under a normal outward tension they are maintained in contact with the conducting surfaces thereof to complete thecircuit through coating 12d.

Unlike the embodiment shown in FIG. 5, the internally coated column does not require an external insulator coating for protection against'electric shock from the resistance coating 12d. Of course, if desired, a protecting coating such as 19a may be applied to the external aims i1 periphery of the column lla, but this is not necessary as in the other case.

A still further modification of the present invention is shown in FIG. 7, wherein a column ila is coated both internally and externally with resistance material. The external coating 12c joins the internal coating 12d at the lower open end of the column as at 12c, and while this is shown as a separate connecting coating of resistance material, the two coatings can be simply continuous around the lower end of the column.

-In this form, the external peripheral grooves 152 and the internal peripheral grooves 15f are arranged at the same end of the column in staggered relation, the external grove 15a receiving one contact ring 17c and the internal groove 15 receiving the other contact ring 17d. Thus, upon energizing the contact rings 17c and 17d, the circuit is completed and envelopes the entire inner and outer peripheral surfaces of the column. Inasmuch as the column in FIG. 7 is provided with an external resistance coating 12c, it is necessary to apply an insulating coating 1% thereto which, preferably, extends around the lower end of the column wall and partly into the interior thereof as at 190.

It will be apparent that with any of these groove arrangements on column-like glassware, the metal wraparound connector band such as shown in FIG. 13 of the copending application, is not necessary as the spring contact rings automatically retain themselves in place within the grooves.

The basic principle of operation in all of the foregoing embodiments of this invention is substantially the same, and it will be understood that these are simply illustrative of numerous possible adaptations of the invention. It will be apparent that by providing an electrical resistance film or coating which will not crack or peel off, such as a noble metal bonded to the surface, and arranging said coating in an electrically conducting circuit in the form of broad bands or strips which either are discontinuous around the periphery in that they have one or more splits or bare areas which define the circuit boundaries, or, covering the whole periphery, are provided with integral electrically contacting shunt/ distributor configurations at selected locations between the terminals for the purpose of providing a controlled pattern of heat intensity and not acting solely as terminals, or discontinuous bands as above together with said shunt/distributor configurations, and having terminal means for positively locating and retaining electrical contacts, that units of glassware and the like may be heated under controlled and safe conditions. The

protective jacket of bonded electrical insulation which is unnecessary at explosion-safe voltages below 6 volts for Underwriters Class 1, Group D, service, also is heat and chemical and abrasion resistant, and with the provision of support-clamp contact electrodes affords a pnactical and very conveniently handled article of laboratory heating glassware or the like, the temperature of which can be raised to 700C. in at least one of its forms.

It is within the scope of the present invention to employ a continuous band with or without shunts, terminating in one or more grooves capable of utilizing a single piece contact clamp such as illustrated in FIG. 12 of said copending application.

In the claims, the term article of glassware or the like is intended to include glass coated, or vitreous enamelled metal and similar materials as a base for the resistance coating.

From the foregoing, it is believed that the invention may be readily understood by those skilled in the art without further description, it being borne in mind that numerous changes may be made in the details disclosed without departing from the spirit of the invention as set fonth in the following claims.

We claim:

1. A hollow article of glassware or the like, having at least one peripheral surface thereof provided with an uninterrupted coating of an electrically conductive material forming a resistance band, said peripheral surface being annularly recessed to provide at least one terminal groove, electrical conducting material lining said groove in electrical contact with said resistance coating, contact means engaging said groove and electrically connecting said groove lining material to a source of electricity to provide a first terminal for said coating, and terminal means to complete an electrical circuit through said resistance coatmg.

2. A hollow article of glassware or the like, having at least a portion of its external peripheral surface coated with an electrically conductive material forming a resistance band, said external peripheral surface being annularly recessed at the vertical extremities of said coating to provide two terminal grooves, electrical conducting material lining said grooves in electrical contact with s-aid coating, and contact means engaging said grooves and electrically connecting said groove lining material to a source of electricity to provide terminal means for the extremities of said coating to complete an electrical circuit through said coating.

3. A hollow article of glassware or the like, having at least a portion of its internal peripheral surface coated with an electrically conductive material forming a resistance band, said internal peripheral surface being annularly recessed at the extremities of said coating to provide two terminal grooves, electrical conducting material lining said grooves in electrical contact with said coating, and contact means engaging said grooves and electrically connecting said groove lining material to a source of electricity to provide terminals for said coating to complete an electrical circuit through said coating.

4. A hollow article of glassware or the like, having adjacent portions of both its internal and external peripheral surfaces continuously coated with an electrically conductive material forming a resistance band, said peripheral surfaces being annularly recessed at the adjacent extremities of the respective coated surfaces to provide terminal grooves, electrical conducting material lining said grooves in electrical contact with said coating, and contact means engaging said grooves and electrically connecting said groove lining material to a source of electricity to provide terminals for said coating to complete an electrical circuit through said coating.

5. An article of glassware as claimed in claim 1, wherein said coating of conductive material is enveloped by a coating of insulating material.

6. An article of glassware as claimed in claim 1, wherein said terminal groove is coated with a material of lesser resistance than that of said conductive coating.

7. Apparatus as claimed in claim 1, including a resilient contact ring engageable with said groove, connecting said lining material to a source of electricity.

8. A hollow article of glassware or the like, having at least one peripheral surface thereof provided with an uninterrupted coating of an electrically conductive material forming a resistance band, said peripheral surface being contoured at at least one extremity to receive an electrical connector, said contoured area being coated with an electrical conducting material in electrical contact with said resistance coating, contact means engaging said contoured area and electrically connecting the same to a source of electricity to provide a first terminal means for said surface coating, and terminal means to complete an electrical circuit through said resistance coating.

References Cited by the Examiner UNITED STATES PATENTS 1,978,089 10/34 Jones 219-432 2,761,945 9/56 Colbert ct a1 219-536 2,833,307 4/59 Orr 219-496 3,050,608 8/62 De Woody 219-547 3,092,704 6/63 De Woody ct al 219-385 RICHARD M. WOOD, Primary Examiner. 

1. A HOLLOW ARTICLE OF GLASSWARE OR THE LIKE, HAVING AT LEAST ONE PERIPHERAL SURFACE THEREOF PROVIDED WITH AN UNINTERRUPTED COATING OF AN ELECTRICALLY CONDUCTIVE MATERIAL FORMING A RESISTANCE BAND, SAID PERIPHERAL SURFACE BEING ANNULARLY RECESSED TO PROVIDE AT LEAST ONE TERMINAL GROOVE, ELECTRICAL CONDUCTING MATERIAL LINING SAID GROOVE IN ELECTRICAL CONTACT WITH SAID RESISTANCE COATING, CONTACT MEANS ENGAGING SAID GROOVE AND ELECTRICALLY CONNECTING SAID GROOVE LINING MATERIAL TO A SOURCE OF ELECTRICITY TO PROVIDE A FIRST TERMINAL FOR SAID COATING, AND TERMINAL MEANS TO COMPLETE AN ELECTRICAL CIRCUIT THROUGH SID RESISTANCE COATING. 